The present invention relates to a swash plate compressor which is suitable for use in a vehicle air conditioner.
A swash plate compressor of the type carries out a compressing operation by converting a rotational force of a swash plate into a reciprocating motion of a piston via a sliding member held to the piston. In the swash plate compressor, the swash plate extends along a reference plane and has a sliding surface which faces on the sliding member with rotation of the swash plate in the manner known in the art. Accordingly, it is required to lubricate between the sliding member and the swash plate.
In swash plate compressors, for use in vehicle air conditioners, whose reduction in size and weight have been required, the supply of lubricating oil to the sliding members is reduced during low-speed operations of vehicle engines. Accordingly, there have been proposed various lubrication mechanisms for preventing load increases and burning of the sliding members.
For example, Japanese Examined Patent Publication No. 63-27554 has proposed a technique wherein surfaces of sliding members contacting a swash plate are formed into gradually or gently curved surfaces to obtain gaps therebetween so that oil films are held in the gaps to improve lubrication characteristics for the sliding members. In the technique, the surface of the sliding member slidably contacting the swash plate is constituted of a plurality of curved surfaces including a gently convex curved surface with a large radius of curvature obtained by numerically defining heights thereof setting its central portion as the apex, and round portions smoothly continuous with the convex curved surface. It is known that the convex curved surface and the round portions are essential and the relationship thereof influences the lubrication efficiency.
In the foregoing conventional technique, however, the lubrication effect for the sliding members is insufficient and unstable. Specifically, since the shape and roughness of the convex curved surface and the round portions largely influence the lubrication, it is difficult to accomplish the performance as designed.
Further, since the surface of the sliding member slidably contacting the swash plate is constituted of the curved surfaces having different curvatures, the formation process thereof is not simple. Moreover, since the lubrication effect delicately changes depending on the curvatures of the curved surfaces as described above, the laborious process and the accurate technique are required.
Since it is complicate to form the sliding surface by two curves with different curvatures like the foregoing sliding member, much difficulty is encountered from a technical point of view.
Particularly, since it is necessary to manufacture a plurality of relatively small sliding members each requiring accuracy, much time and effort for ensuring dimensional accuracy are required. Thus, not a small burden is required on quality control, which leads to an increase in cost.
As described above, it is difficult to achieve the lubrication effect for the sliding members as designed. For maintaining the delicate gaps, the maintenance including cleaning is required on a constant basis.